Process of manufacturing benzoate.



UNITED STATES PATENT oEEIoE.

EDWIN O. BARS'IOW, 0F MIDLAND, MICHIGAN, ASSIGNOR TO THE DOW CHEMICAL COM- PANY, OF MIDLAND, MICHIGAN, A CORPORATION OF MICHIGAN;

PROCESS OF MANUFACTURING BENZOATE.

Specification of Letters Patent.

Patented Nov. 9, 1 909.

No Drawing. Original application filed October 25, 1905, Serial No. 284,492. Divided and this application filed Karen 14, 1906. Serial No. 305,958.

To all whom it may concern:

Be it known that I, EDWIN O. BARSTOW, a citizen of the United States, resident of Midland, county of Midland, and State of Michigan, have'invented a new and useful Improvement in Processes of Manufacturing Benzoates, (Case 13,) of which the following is a specification, the principle of the inven tion being herein explained and the best mode in which I have contemplated applying that principle, so as to distinguish it from other inventions.

My invention relates to processes of making benzoic acid and benzoates, the particular subject-matter described and claimed herein being dividedout of a pending application for U. S. Letters Patent No. 284,402, filed October 25, 1905. Said invention consists of steps hereinafter fully de scribed and specifically set forth in the claims.

The following description'sets forth in detail certain steps embodying my invention, such disclosed steps constituting but one of various ways in which the principle of the invention may be used.

Some of the various methods by which benzoic acid and benzoates have heretofore been manufactured are as follows: (I) from gum benzoin and other natural gums by sublimation or extractlon, such processes involving the treatment of the gum simply with" heat, or with an alkaline solution to dissolve thebenzoic acid, and the subsequent precipitation by means of a mineral acid. (2) From urine and hippuric acid by wellknown processes. ,(3) From benzyl chlorid, benzal chlorid or benzo-trichlorid, by the following processes: (a) Ijrom benzyl chlorid by oxidation with hot dilute nitr c ac d, g1V- ing as resultant products benzolc acid and hydrochloric acid. (6) From benzal chlorid as a by-product in the manufacture of benzaldehyde, the benzal chlorid being treated with a solution of lime. From benzo-tri-chlorid by heatin with water under pressure, With lime an water or a solution of caustic soda and Whiting.

My invention relates to those of the above- 50. mentioned methods in which benzoic acid or l the benzoates are manufactured from homoand particularly to that method in which sodium benzoate is manufactured from benzyl chlorid, although the broad spirit of my invention comprehends the manufacture of sodium and other benzoates; also, the manufacture of benzoates from benzal chlorid; from benzyl alcohol, benz aldehyde, and other products intermediate of the chlorination products of toluene and benzoates, as is particularly pointed out and claimed inimy pending app ication for U. S. LettersPatent, Serial No. 284,402, hereinbefore mentioned, and ma second pending application (Case C) filed even date herewith. When manufactured by the old method noted above from benzyl chlorid, the old process has been subject to the difliculty that the nitric acid is an expensive oxidizer and corrosive so that glass orstoneware ap aratus is required and theprocess as a who e has been found unsuitable for commercial purposes. As manufactured b the old method noted above from benzal ch orid, benzoic acid and the benzoates are obtained as by-produc-ts only, which is unsatisfactory when the main purpose sought is the manufactureof benzoic acid or benzoates. When manufactured b the old method noted above from benzo-tn chlorid, the old process is subject to the .difiiculty that the resultant product always contains im ure acids in the form of chlorbenzoie'aci s.

In the carrying out of my improved process 'I produce a chlorin substitution product of one of the homologues of benzene, such product having only one side chain,'and then ing chlorin. However, I may start with the chlorin substitution product and in that case my improved process would consist of only one step, viz., the oxidation of such product by the, chlorin-containing compound. In order to typify the methods by which my process may e effected I shall describe the same as carried out when I manufacture that .de-

rivative of toluene which has one atom of chlorin in one side chain, viz.,benzyl chlorid, and then oxidize the same by heating with a solution obtained by absorbing chlorin in a cold solution of sodium hyg'rate, suflicient excess of sodium hydrate ing present to stage, either benzyl chlorid or a chlor-toluene cule of the toluene to take one atom of the .it forms a chlor-toluene.

very little ring chlorin, whatever it does hold chlorin; It will be understood, therefore, 7 that if ll pass into the toluene only such a each molecule with one atom, substantially neutralize the hydrochloric acid and benzoic acid formed in the reaction. It will be understood, however, that other compounds may be utilized without departing from the spirit of my invention.

When toluene is chlorinated to the first is formed and the tendency is for each molechlorin before any molecule takes a second atom, this atom of chlorin going into the side chain or methyl radical of the toluene in a great majority of cases, if the conditions under which the chlorination takes place are proper, such conditions being principally that the chlorination be aided by heat and take place in the sunlight. If the chlorination is effected in the cold and dark, or there be present any carrier such as iodin or ferric chlorid, the chlorin will tend to go into the ring and not into the side chain. This tendency of each molecule to take up an atom of chlorin before any molecule takes up its second atom is probably due tothe fact that the toluene is more volatile than either benzyl chlorid or chlor-toluene, so '7 that as the chlorin bubbles up through the liquid under treatment, the toluene vaporizes and thus comes into more intimate contact with the chlorin than does the part still remaining as a liquid. When the chlorin atom that is taken up goes into the side chain, it forms benzyl chlorid, and when it goes into the ring, as it does in a comparatively few cases, This chlor-toluene will not form a benzoic acid when treated according to my process, sothat it will not form an impurity in my resultant product. I therefore obtain a benzoate which holds being obtained from those few moleculesof toluene which took up two atoms of chlorin, of which two atoms one went into the ring and one into the side chain; because, if both of the chlorin atoms or all three of them, if some molecules of toluene had taken up three atoms, had gone into the ring, they would not form a benzoic acid at all, or, if they had gone into the side chain, they would have formed a benzoic acid containing no ring quantity of chlorin as is necessary to furnish all of such toluene will be chlorinated to the first stage in the manner described above, and by tar the greater part of it will be in the form of benzyl chlorid, the remaining smaller part being in the form of chlor-toluene, which latter is inert, when l oxidize, as hereinafter fully described, and, consequently, does not form a chlor-benzo'ic acid which vwould be an impurity in the resultant product. It will be seen, therefore, that if I l should chlorinate the toluene to the second or third stage, the probabilities would be vhich chlorin had entered both the ring and the side chain of the toluene, and thus result, when the oxidation is effected, in the production of a chlor-benzoic acid, as noted above. Another objection to the chlorination of the toluene to the second stage, viz: to benzal chlorid or to the third stage, viz: to benzo-tri-chlorid, is that much more apparatus is required to treat a given amount of toluene in a given time, which is uneconomical since the chlorination of toluene is at the best a delicate and comparatively expensive operation. Furthermore, the rate of absorption of the chlorin is much faster during the first stage of the chlorination than it is during the later stages; also, the loss due to decomposition is not nearly so great when benzyl chlorid is formed as it is when benzo-trichlorid is formed, due to the fact that the liquid remains in the apparatus less than one-third as long, and also to the fact that under the conditions, benzo-tri-chlorid decomposes more readily than benzyl chlorid.

My improved process then consists in chlorinating toluene to the first stage, viz. to benzyl chlorid and then heating the latter with a. solution obtained by absorbing chlorin in a sodium hydrate solution, and containing an excess of sodium hydrate sufiicient to neutralize the acids set free during the oxidation, sodium benzoate thus being formed. If the chlorination has reached the second stage, sodium benzoate may be obtained from the benzal chlorid by treating the latter in the same manner as the benzyl chlorid above.

As a guide in practically working out my process, the following data, illustrating the c n on cwanaoci euaonz C H C0ONa+3NaCl+2H,O.

reatly increased of obtaining a product in The apparatus preferably employed consists of a common cement-lined iron retort provlded with a reflux condenser, an agitator, and direct steam and water connections for regulating the temperature. The preferred temperature is about 95 Q.

When chlorin is absorbed in a cold solution of sodium hydrate, sodium chlorid and benzoates, for instance, converting benzyl sodium hypochlorite are formed in equal chlorid molecular proportions; thus,

QNaOH-l-Cl,:NaCl-l-NaOCl-l-ILO.

The sodium hypochlorite is then the oxidizing constituent of the solution. In oxidizing a derivative of toluene with a hypochlorite, it is necessary to have something present to neutralize the acid set free as soon as formed, for otherwise such acid will tend to decompose the unstable hypochlorite with the formation of chlorid and chlorate with libera tion of chlorin, and consequent poor yield of benzoic acid. While in the illustration given I ha \e used sodium hypochlorite as the oxidizing agent, I can use other hypochloritecontaining substances, for instance, the solution obtained by absorbing chlorin in a solution of potassium hydrate. The use of alkaline earth hypochlorites, such as bleaching powder, has been particularly pointed out and claimed in my pending application, Serial No. 284,402, hereinbefore mentioned. Although in the illustration given I use sodium hydrate to neutralize the acid set free by the oxidation, other substances capable of neutralizing acids, such as potassium hydrate, sodium carbonate, etc., may be used. Furthermore, I prefer to use toluene as the source of benzoic acid, but any of the hoinologues of benzene containing one side chain will serve the purpose. The gist of my invention, then, consists in the oxidation of the derivatives of members of the benzene series of hydrocarbons by means of a solution containing an alkaline hypochlorite, such derivatives, as benzyl chlorid, benzal chlorid, benz-aldehyde, benzyl alcohol or any of the side chain derivatives of the homologues of benzene which require oxidation to form benzoic acid, being obtained in any desirable way.

It will be noted that while I prefer to stop the chlorination of the toluene at the first stage, viz., at the formation of benzyl chlorid, it is not necessary to do so, but that I can stop at any point short of the complete com-'ersion to benzo-tri-chlorid, such chlorinated toluene then belng 1n the form of a mixture of toluene, benzyl chlorid, benzal chlorid,benzo-tri-chlorid,and small amounts of decomposition products and compounds with chlorin in the ring, this mixture, upon being treated with a solution of sodium hypochlorite and sodium hydrate, being oxi-.

dized directly to sodium benzoate without further chlorination, which further chlorination' would give aproduct yielding a less pure benzoate. I prefer to treat the chlorinated toluene directly with the hypochloritecontaining substance, but I might convert the chlorids of toluene into intermediate products, and then oxidize the latter to not applicable thereto.

1 or'similar elements or radicals.

into benzyl alcohol by heating with a solution of sodium carbonate or by any other suitable method, and 0011- verting benzal chlorid into benz-aldehyde with a lime solution, and then oxidizing the benz-aldehyde into benzoic acid by means of an alkaline hypochlorite. This method has been fully described and claimed in my pending application for U. S. Letters Patent filed even date herewith Serial N 0. 305,959, filed March 14, 1906. Benzo-trichlorid does not require any oxidation to form benzoic acid and hence my process is By my improved process I obtain a pure benzoic acid, due to the small percentage of chlorinated toluene which contains its chlorin both in the side chain and in the ring; furthermore, in order to obtain a given amount of benzoates, I require less than one-third of the apparatus and only one-third of the amount of chlorin gas that has been necessary heretofore when the toluene was converted into benzo-trichlorid, the remaining oxidation being easily and cheaply efi'ected by means of a solution of sodium hypochlorite and sodium hydrate.

It has been stated that the class of compounds which my improved process is adapted to utilize as a starting point for the oxidation step, that constitutes the process proper, is merely exemplified in the benzyl chlorid. The members of the general class of compounds available for use in the process may be appropriately denominated sidechain substitution products of'a member of the benzene series of hydrocarbons, where by such term- I mean hydrocarbon derivatives in which one or more hydrogens of a side-chain have been replaced either directl or indirectly by chlorin, oxygen, hydroxy Thus in its specific aspects the present application deals with a side-chain substitution product in which chlorin figures as the substituting element; while in the companion application, Serial No. 305,959, referred to above, a product in which the hydrogen is similarly replaced by hydroxyl is employed. The sub-type of product exemplified 1n the latter case, while includedin the generic term above defined, has for'the purpose of such companion application been called a artially oxidized, oxygen-containing pro not of a member of the'benzene series-of hydrocarbons. i

Having thus described my invention in detail,v that which I particularly point out .and distinctly claim, is:

1. In a process of manufacturing benzoates, the step which consists in oxidizingto the acid a side-chain substitution product of a member of the benzene series of hydrocarbons, by means of a chlorin-containing reagent in the presence of a hydrate of an I bons by means of a chlorin-contammg re agent in the presence of sodium hydrate and water.

3. In a process of manufacturing benzoates, the step which consists in oxidizing to the acid a side-chain substitution product of a member of the benzene series of hydrocarbons, by means of sodium hypochlorite in the presence of sodium hydrate and'water.

4. In a process of manufacturing benzoates, the step which consists in oxidizing to the acid a chlorinatedderivative of a member of the benzene series of hydrocarbons, by means of a chlorin-containing reagent in the presence of a hydrate of an alkalimetal and a suitable'solvent. V

5. In a process of manufacturing benzoates, the step which consists in oxidizing to the acida chlorinated derivative of a mem: ber of the benzene'series of hydrocarbons,

' by means of a chlorin-containing reagent 1n -the presence of sodium hydrate and water.

'6. In a process of manufacturing benzoates, the step which consists in oxidizing to- I ,the acida chlorinated derivative of a mem- 1 heating.

ber, of the benzene series of hydrocarbons,

benzyl chlorid to the acid by means of a chlorin-containing reagent in'the presence of sodium hydrate and water.

9. In .a process of manufacturing benzoates, the ste which consists in oxidizing benzyl vchlor1d tothe acid by means of sodium hypochlorite in the presence of sodium hydrate and water. p

10. The process of manufacturing benzoates which consists informing an emulsion of benzyl chlorid with water, mixing such emulsion with'a solution of sodium hypochlorite to which a quantity of sodium hydrate has been added, and thereupon Signed by me this 10th day of March EDWIN O. BARSTOIV. Attested by WM. L. BAKER,

EDW. A. LANE. 

